Thermal circuit breaker



Oct. 4, 1949.

J. KITMAN THERMAL CIRCUIT BREAKER Filed Jan. 2, 1948 Patented Oct. 4, 1949 UNITED STATES PATENTOFFICE THERMAL CIRCUIT BREAKER Julia Kitman, Pittsburgh, Pa.

Application January 2, 1948, Serial No. 119

1 Claim.

This invention relates to an electric circuitbreaker, and important objects and advantages thereof are to provide a circuit-breaker of the character described, which is designed and intended to supersede a fuse plug of the conventional type commonly used in branch circuits carrying the smaller currents, which will function automatically to break the circuit when the current strength reaches a certain predetermined value, which may be reset for repeated use, which is simple in its construction and arrangement, durable and eflicient in its use, positive in its action, and comparatively economical in its manufacture and use.

With the foregoing and other objects in view which will appear as the description proceeds, the invention resides in the novel construction, combination, and arrangement of parts herein specifically described and illustrated in the accompanying drawing, but it is to be understood that changes in the form, proportions and details of construction may be resorted to that come within the scope of the claims hereunto appended.

In the drawing wherein like numerals of reference designate corresponding parts throughout the several views;

Figure 1 is a side elevational view, partly in cross section, of the improved electric circuitbreaker, with the embodied control mechanism in the operative position.

Figure 2 is a similar view, with the control mechanism in the inoperative position.

Figure 3 is a top plan view of the device.

Referring in detail to the drawing, the improved electric circuit-breaker comprises a hollow plug body I, including a top cover 2, which latter is fixed to the plug body by cementing, or in any other suitable manner. The lower exterior portion of the plug body is surrounded by a fixed metallic thread shell 3, and the bottom 4 of the plug body carries a fixed contact pin 5 disposed centrally of the bottom.

The plug body I and the top cover 2 are constructed of any suitable insulating material, and the assembly of the plug body and top cover, together'with the embodied thread shell 3 and contact pin 5, provide a plug structure which has a general contour identical to the conventional type of fuse plug, and which is designed and intended to be screwed into the conventional type of electrical socket.

A thermostatically controlled switch 6 is mounted in the plug body I, and comprises a pair of vertically opposed contact members 1 and 5 The lower contact member I is carried by a contact bracket 9, which is fixed to the contact pin 5. The upper contact member 8 is carried on the lower face of the outer end of a horizontally disposed contact bar 10. The contact bar has a tapered inner end H, and is pivotally connected by a pivoting pin l2 to the lower end of a supporting bracket l3. The latter is secured to and depends from the top cover 2.

A spiral compression spring i4 is connected with the supporting bracket l3 and with the outer end of the contact bar I0, and normally functions to shift and hold said contact bar to an angular position from the horizontal to open the switch 6, as clearly shown in Figure 2. The angular shiftable movement of the contact bar is limited by a shoulder it formed in the support bracket [3.

A push button it is mounted for vertical movement in a centrally disposed opening il in the top cover 2. 1i spiral spring 88 is nounted in the opening I! and surrounds the push button. The action of the spring l8 normally tends to shift the push button to its upward position in the opening ii.

A manually actuated switch I9 is mounted in the plug body 3, and comprises a pair of vertically opposed contact members 20 and 2|. The upper contact member 20 is carried by the top cover 2, and the lower contact member 2i is carried by a bimetallic latch arm 22.

The bimetallic latch arm 22 is thermostatically actuated, and has its upper end secured to the lower end of the push button IS. The latch arm is normally vertically disposed in the plug body i, and carries a fixed tapered latching element 23 on the inner side of the lower end portion thereof. The latching element normally engages the tapered end II, of the contact bar [0, for holding the latter in the normal horizontal position against the pull of the spring I, to maintain the thermostatically actuated switch 6 in the closed position, as shown in Figure 1.

A flexible conductor 24 connects the inner end of the contact bar [0 with the lower end of the latch arm 22, and a flexible conductor 25 connects the upper end of the latch arm with the thread shell 3 of the plug body. It will here be noted that either or both of the conductors 24 and 25 may be constructed of material that will fuse to break the electric circuit when the current strength reaches a predetermined value.

circuit is completed through the contact pin I, the contact bracket I, the closed switch I, the contact bar it, the conductor 2t, the latch arm 22, the closer switch I9, the conductor 25. and the thread shell 3. Under normal conditions the switches 6 and I! are always closed to maintain the circuit, by the engagement of the contact bar Ill by the latching element 28.

The construction and operation of the bimetallic latch arm 22 is such that if the current strength of the circuit reaches and exceeds the predetermined value, the latch arm will be thermostatically actuated to release the latching element 23 from the tapered end ll of the contact bar ill, whereby the latter will be shifted by the action of the spring I to open the switch and thereby break the circuit.

To reclose the circuit, the push button It is depressed to lower the latching element 23 so that the latter will reengage the tapered end ll of the contact bar I0. Upon release of the push button, the spring i8 will elevate the again normal latch arm 22 and cause the latching element 23 to reengage the contact bar and shift the latter to the normal horizontal position to close the switch 8 and thereby complete the circuit.

Due to the inherent resiliency of the latch arm 22, and to the tapers of the contact bar end Ii of the latching element 23, the reengagemnt of the latter with said end ii is readily effected by snap action.

When the push button It is depressed to reclose the switch 6, in the manner stated, the switch i9 is opened for safety purposes, as the circuit is not closed until pressure upon the push button is removed to cause the closing of the switch is by the action of the spring I 8. The construction and arrangement of the switch I! limits the upward movement of the push button in the top cover opening l1, and thereby obviates the possibility of holding a closed circuit by exerting suilicient upward pull manually on the push button to prevent the normal thermostatic operation of the switch 6 to break the circuit when required for safety.

The present invention provides a most durable and eillcient device of its kind, which may be 4 nomically employed for the purpose and in the manner herein set forth.

What I claim is:

An electric circuit-breaker of the class described, comprising the combination ofhollow plug body including a top cover, a thread shell surrounding the lower portion of said body, a contact pin secured in the bottom of said body. a thermostatically controlled switch mounted in said body, a manually controlled switch mounted in said body, a push button shiftably mounted in said cover, a spring mounted on said button for normally maintaining the latter in the upward position, a contact bracket secured to said pin and being connected with said thermostatically controlled switch, a supporting bracket carried by said cover, a contact bar pivotally connected with the lower end of said supporting bracket and being connected with said thermostatically controlled switch, a bimetallic latch arm carried by said button, a latching element carried at the lower end of said arm and normally engaging one end of said bar for maintaining said thermostaticall controlled switch in the closed position, a spring connected with said supporting bracket and with said bar for shifting the latter to open said thermostatically controlled switch when said element is released from said bar by the thermostatic action of said arm, said manually controlled switch including a pair of contact members, one of said pair of contact members being carried by said cover, and the other of said contactmembers being carried by said arm, and means formed on said supporting bracket for limiting the shiftable movement of said bar, a conductor connecting said bar with said arm, and a conductor connecting one of said pair of contact members with said shell.

JULIA MAN.

cheaply manufactured and successfully and eco- REFERENCES CITED The following references are of record in the file of this patent: 

